Page 9 - Circulatory System in Finfish

Sinus venosus: The first chamber is called the sinus venosus, it is the

preliminary collecting chamber. In teleosts it is filled from two major

veins called the hepatic veins and the left and right branches of the

Curvierian ducts which in turn collect blood from the paired (left and

right) lateral veins the inferior jugulars, the anterior cardinals and the

posterior cardinals. However in the elasmobranchs only one hepatic

vein leads into it.

Atrium. From the sinus venosus the blood flows into the atrium. the

atrium is the largest of the chambers and weakly muscular. It pushes

the blood, with weak contractions in the ventricle.

Ventricle. The ventricle is the only well muscled chamber, nearly as

large as the atrium it is the work horse of the heart, its contractions

drive the blood around the body.